1. Field of the Invention
The present invention relates to a filament winding method and a filament winding apparatus.
2. Description of the Related Art
A known filament winding apparatus includes a hoop winding device and a helical winding device, and winds a fiber bundle around a periphery of a liner to form a reinforcement layer by repeatedly performing hoop winding and helical winding alternately with respect to the liner (e.g., US Patent Publication No. US/2010/032510A1).
In a conventional hoop winding device, when the hoop winding is finished, the hoop winding device is moved to a retreated position located away from the liner with the hoop-wound fiber bundle still connected to a liner surface. The helical winding is then carried out over the hoop winding, and when the helical winding is finished, the hoop winding device is moved to a position to start the next hoop winding. In this case, the movement is started while carrying out easy winding from the retreated position. Easy winding is a winding method carried out when moving the hoop winding device while winding the fiber bundle, and the easy-wound fiber bundle is not involved in the formation of the reinforcement layer.
After the hoop winding device is moved to an end of the liner while performing the easy winding, the hoop winding device starts combination winding. Combination winding is a winding method of gradually moving a winding position of the fiber bundle to a hoop winding starting position while alternately winding the fiber bundle around both ends of the liner a plurality of times (e.g., Japanese Unexamined Patent Publication No. 2009-174700).
Combination winding is carried out because the fiber bundle slips and cannot be wound even if the hoop winding is carried out at an inclined portion such as a dome portion of the liner. Thus, the fiber bundle can be wound around the dome portion by winding the fiber bundle at an angle of pulling the fiber bundle in an axial direction of the liner by combination winding, and the angle is gradually changed to the angle of hoop winding at a tubular portion of the liner where the fiber bundle does not slip.
As described above, in a conventional filament winding apparatus, since hoop winding and helical winding are continuously performed, the hoop-wound fiber bundle remains connected to the liner surface without being cut when the hoop winding is finished and the helical winding is to be carried out next. Therefore, an operator is not required to fix the fiber bundle to the liner surface by manual operation when carrying out hoop winding next.
However, when helical winding is finished and the next hoop winding is to be carried out, the hoop winding device is moved while carrying out easy winding and combination winding of the fiber bundle from the retreated position to the hoop winding starting position. Thus, if the hoop-wound fiber bundle remains connected to the liner surface without being cut, the time to carry out easy winding and combination winding of the fiber bundle becomes necessary, which may lengthen the time required for hoop winding. Easy winding and combination winding of the fiber bundle are hardly involved in the formation of the reinforcement layer of the liner. Thus, an excessive fiber bundle is used, which may lead to increase in manufacturing cost.